Before you start chasing the solenoid or pulling the tranny cover, you should
check the switch in the gear shift. It is prone to corrosion. Inside the switch
is a rolling contact that rolls onto two contact surfaces. Over time, the roller
and contacts tend to corrode and you will get intermittent engagement of the OD.
The easiest way to diagnose this is to remove the shift knob to reveal two wires
that connect to the switch. Connect the two wires together thus by-passing the
switch. Take the car for a run to see if the OD engages and stays engaged. You
can open and close the circuit to check for consistent operation. If this works
OK, your problem is in the switch. You can very carefully open the switch by
prying the bent over tabs. Take care as there is a spring inside that will fly
off into "Never to be Found Land". You can clean the surfaces with fine emery
paper and reassemble. Or buy a new switch (too much money).
If the shifting is still erratic with the wires joined together, then you can
start looking at the solenoid on the firewall, 3rd/4th gear switch on the
tranny, then the solenoid. The solenoid can also have pitted and corroded
contacts inside and is also easy to open and clean the contact inside with the
same emery paper. The tranny switch and solenoid require significantly more
effort to get at and replace so leave these to the last. You may even find an
intermittent wiring connection during the early process and save a lot of work.
Vic Whitmore
76 Spitfire
Thornhill, Ontario
Mark Gardner wrote:
>
> Hi all - I'm going to look at a '79 spit with O/D tomorrow. The owner
> sayd the O/D is intermittent - sometimes it engages and sometimes it
> doesn't. He says it is almost certainly a solenoid. He says he has the
> solenoid, he just hasn't installed it yet.
>
> 1. Is there an easy way to troubleshoot this on the spot?
> 2. Is this a common problem, or am I likely getting into something
> major?
> 3. If it is the solenoid, can this be changed with the gearbox still in
> the car?
>
> Thanks in advance,
>
> Mark Gardner
> (Looking at #14 tomorrow)
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